Rotavirus genotype distribution during the pre-vaccine period in Bolivia: 2007-2008

Abstract

Objectives: Rotavirus is the most important etiology of severe diarrhea in Bolivia. The monovalent attenuated human oral rotavirus vaccine Rotarix(®) was introduced in Bolivia in 2008. We describe the molecular epidemiology of circulating rotavirus strains before vaccine introduction.

Methods: Two thousand one hundred thirty-five diarrheal samples were collected from hospitals in four Bolivian cities during 2007-2008. Forty-three percent (445 of 1030 rotavirus-positive samples) were analyzed for G and P genotypes. Among those, 331 were electropherotyped by polyacrylamide gel electrophoresis. Disease severity was quantified using a modified Vesikari scale.

Results: Among the 445 samples, five genotypes were found to be prevalent: G9P[8] (33%), G1P[6] (17%), G2P[4] (13%), G9P[6] (12%), and G1P[8] (4%). Co-infections with two or more strains accounted for 14% of samples. The most prevalent strain, G9, showed greater electropherotype diversity compared to other serogroups. Strain G1P[6] generally infected younger children and peaked later in the year than other strains. No particular genotype was associated with a higher severity score, though there was a significant difference in the duration of diarrhea between genotypes.

Conclusions: During the 2-year pre-vaccine period, substantial diversity of rotavirus co-circulating strains was observed. These data constitute a baseline against which changes in circulating strains post-vaccine introduction can be monitored.

Keywords: Epidemiologic surveillance; Molecular epidemiology; Pediatric diarrhea; Pediatric infectious diseases; Rotavirus.

Figure 1

Genotype distribution 2007–2008. Five genotypes predominated during the surveillance period, and G1P[6], G1P[8], and G2P[4] showed considerable variation by year.

Figure 2

Two genotypes, G1P[6] and G9P[6], had peaks outside the primary rotavirus peak (April to July). Lines represent the number of cases per month (month 1 = January, 2 = February, etc.) for each genotype as a percentage of the total number for that genotype for the period 2007–2008.

Figure 3

G9P[6] and G9P[8] showed greater electropherotype diversity than other genotypes. Bars represent individual electropherotypes as a percentage of the total electropherotypes detected for each genotype (i.e., total bars for each genotype should add up to 100).